My top three chapters are, Show and Tell, Dialogue Mechanics, and Interior Monologue. Show and Tell teaches you to put your story into action scenes, to show it, not to narrate or tell it. The authors use a scene from The Great Gatsby to get their point across.

Gatsby is of course a great novel. But, several parts of Gatsby are
told in narrative summary. The authors show you the difference between
telling and showing by taking a specific narrated scene and changing it
into a scene that shows. The scene comes to life. The original scene is
a second hand report, while the rewritten scene shows it happening now.

Every writer wants to write great dialogue. Something that gets the
reader's heart racing. As the authors note, writing dialogue is more
challenging than writing narration or even action scenes. Dialoque
Mechanics teaches you how to make your characters come alive with what
they say and how they speak. The authors also show you how to write
dialogue without associated tag lines, like.

"There's really no way that could have happened," she said sarcastically.

"That's not possible!" she said.

Thereby teaching you to resist the urge to explain, or R.U.E, as they say.

Unless your characters are dead, they think; and the best way to get their thoughts across is through Interior Monologue.

The hotel was a block away. Paul knew what was waiting for him when
he got to his room. He could all ready smell her perfume. He hoped she
was wearing the black see-through nightie he'd bought her. The thought
of the silky material against her smooth toned body aroused him.

In this chapter, the authors teach you the power of interior
monologue and how to give out information that you can't put in
dialogue. They also show you how to use it properly and when not to use
it.

After reading Self-Editing For Fiction Writers, I was ready to
tackle the first rewrite of my novel, which I did mostly as narrative
text. As I began rewriting, I could feel the change in my characters.
They suddenly were three-dimensional, they had depth. I turned dull
scenes into action with strong dialogue, and interior monologues that
didn't ramble on.

I've read many books on the art of writing and I truly believe that
Self-Editing For Fiction Writers was the book that helped me to improve
my craft more than any other. It gave me a base from which to expand
and grow as a writer. In fact, it had improved my writing to the point
where I was able to get my first job as a writer.